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                                <section class="normal markdown-section">

                                <h1 id="new-charts">New Charts</h1>
<p>Chart.js 2.0 introduces the concept of controllers for each dataset. Like scales, new controllers can be written as needed.</p>
<pre><code class="lang-javascript">Chart.controllers.MyType = Chart.DatasetController.extend({

});


<span class="hljs-comment">// Now we can create a new instance of our chart, using the Chart.js API</span>
<span class="hljs-keyword">new</span> Chart(ctx, {
    <span class="hljs-comment">// this is the string the constructor was registered at, ie Chart.controllers.MyType</span>
    type: <span class="hljs-string">&apos;MyType&apos;</span>,
    data: data,
    options: options
});
</code></pre>
<h2 id="dataset-controller-interface">Dataset Controller Interface</h2>
<p>Dataset controllers must implement the following interface.</p>
<pre><code class="lang-javascript">{
    <span class="hljs-comment">// Create elements for each piece of data in the dataset. Store elements in an array on the dataset as dataset.metaData</span>
    addElements: <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params"></span>) </span>{},

    <span class="hljs-comment">// Create a single element for the data at the given index and reset its state</span>
    addElementAndReset: <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">index</span>) </span>{},

    <span class="hljs-comment">// Draw the representation of the dataset</span>
    <span class="hljs-comment">// @param ease : if specified, this number represents how far to transition elements. See the implementation of draw() in any of the provided controllers to see how this should be used</span>
    draw: <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">ease</span>) </span>{},

    <span class="hljs-comment">// Remove hover styling from the given element</span>
    removeHoverStyle: <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">element</span>) </span>{},

    <span class="hljs-comment">// Add hover styling to the given element</span>
    setHoverStyle: <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">element</span>) </span>{},

    <span class="hljs-comment">// Update the elements in response to new data</span>
    <span class="hljs-comment">// @param reset : if true, put the elements into a reset state so they can animate to their final values</span>
    update: <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">reset</span>) </span>{},
}
</code></pre>
<p>The following methods may optionally be overridden by derived dataset controllers</p>
<pre><code class="lang-javascript">{
    <span class="hljs-comment">// Initializes the controller</span>
    initialize: <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">chart, datasetIndex</span>) </span>{},

    <span class="hljs-comment">// Ensures that the dataset represented by this controller is linked to a scale. Overridden to helpers.noop in the polar area and doughnut controllers as these</span>
    <span class="hljs-comment">// chart types using a single scale</span>
    linkScales: <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params"></span>) </span>{},

    <span class="hljs-comment">// Called by the main chart controller when an update is triggered. The default implementation handles the number of data points changing and creating elements appropriately.</span>
    buildOrUpdateElements: <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params"></span>) </span>{}
}
</code></pre>
<h2 id="extending-existing-chart-types">Extending Existing Chart Types</h2>
<p>Extending or replacing an existing controller type is easy. Simply replace the constructor for one of the built in types with your own.</p>
<p>The built in controller types are:</p>
<ul>
<li><code>Chart.controllers.line</code></li>
<li><code>Chart.controllers.bar</code></li>
<li><code>Chart.controllers.radar</code></li>
<li><code>Chart.controllers.doughnut</code></li>
<li><code>Chart.controllers.polarArea</code></li>
<li><code>Chart.controllers.bubble</code></li>
</ul>
<p>For example, to derive a new chart type that extends from a bubble chart, you would do the following.</p>
<pre><code class="lang-javascript"><span class="hljs-comment">// Sets the default config for &apos;derivedBubble&apos; to be the same as the bubble defaults. </span>
<span class="hljs-comment">// We look for the defaults by doing Chart.defaults[chartType]</span>
<span class="hljs-comment">// It looks like a bug exists when the defaults don&apos;t exist</span>
Chart.defaults.derivedBubble = Chart.defaults.bubble;

<span class="hljs-comment">// I think the recommend using Chart.controllers.bubble.extend({ extensions here });</span>
<span class="hljs-keyword">var</span> custom = Chart.controllers.bubble.extend({
    draw: <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">ease</span>) </span>{
        <span class="hljs-comment">// Call super method first</span>
        Chart.controllers.bubble.prototype.draw.call(<span class="hljs-keyword">this</span>, ease);

        <span class="hljs-comment">// Now we can do some custom drawing for this dataset. Here we&apos;ll draw a red box around the first point in each dataset</span>
        <span class="hljs-keyword">var</span> meta = <span class="hljs-keyword">this</span>.getMeta();
        <span class="hljs-keyword">var</span> pt0 = meta.data[<span class="hljs-number">0</span>];
        <span class="hljs-keyword">var</span> radius = pt0._view.radius;

        <span class="hljs-keyword">var</span> ctx = <span class="hljs-keyword">this</span>.chart.chart.ctx;
        ctx.save();
        ctx.strokeStyle = <span class="hljs-string">&apos;red&apos;</span>;
        ctx.lineWidth = <span class="hljs-number">1</span>;
        ctx.strokeRect(pt0._view.x - radius, pt0._view.y - radius, <span class="hljs-number">2</span> * radius, <span class="hljs-number">2</span> * radius);
        ctx.restore();
    }
});

<span class="hljs-comment">// Stores the controller so that the chart initialization routine can look it up with</span>
<span class="hljs-comment">// Chart.controllers[type]</span>
Chart.controllers.derivedBubble = custom;

<span class="hljs-comment">// Now we can create and use our new chart type</span>
<span class="hljs-keyword">new</span> Chart(ctx, {
    type: <span class="hljs-string">&apos;derivedBubble&apos;</span>,
    data: data,
    options: options,
});
</code></pre>
<h3 id="bar-controller">Bar Controller</h3>
<p>The bar controller has a special property that you should be aware of. To correctly calculate the width of a bar, the controller must determine the number of datasets that map to bars. To do this, the bar controller attaches a property <code>bar</code> to the dataset during initialization. If you are creating a replacement or updated bar controller, you should do the same. This will ensure that charts with regular bars and your new derived bars will work seamlessly.</p>


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